I have used the 50/2.5 macro lens for botanical
close-up work since 1990, having previously used the
50/3.5 FL and two generations of 50/3.5 FD for that
purpose! I have also used it for medium-scale copying
work (oil paintings), and as a general-purpose lens.
The FL macro was a 4-element lens, and the FD macros,
which I think were optically identical to one another,
were 6-element, in both cases with all elements moving
together during focusing. Not surprisingly, the FD
lenses were better optically than the FL design; it is
my impression that the much more sophisticated design
of the EF lens, with a fixed rear group of correcting
elements behind the main lens ('floating' design), is
even better, although no doubt it is optimised for use
at the smaller apertures usually appropriate for
close-up work. It is highly rectilinear, and the angle
of view is excellent for copying work, where a longer
lens is actually inconvenient. For botanical
fieldwork, the limitation to x0.5 is not a major
problem, and with the MR-14EX ring flash there is no
real issue over working distance and lighting.
Sometimes the perspective given by a longer lens can
be preferable, but on the other hand there are plenty
of situations where you cannot get far enough back
from a plant to allow the use of a longer lens. The
balance of advantage for entomological work is of
course rather different.The Life Size Converter (now discontinued but not hard to find secondhand) is a dedicated optical unit which converts the lens to 70mm focal length and with a range of x0.25 to x1. It works extremely well with this lens, and increases the focal length to almost the same value that the focal length of the 100/2.8 USM macro reduces to as it focuses out to x1. Do not expect the LSC to work well on other lenses; it is not a general-purpose converter. The main drawback of the 50/2.5 is the failure by Canon to update the mechanical side; it is nothing like as well-made as the FD predecessors, uses an AFD motor (so no FTM, which prevents the use of CF-4-1/3 followed by manual fine-tuning), and has no range-limiting switch. Although the lens has an aperture of f/2.5, the reduction in effective aperture in close-up causes the camera to treat it for AF purposes as if the maximum aperture was smaller than f/2.8 but at least f/4, regardless of where it is focused. This and the readiness of the focusing (in the absence of a limiter) to hunt all the way from infinity to x0.5 and back reduces its convenience as a general-purpose lens. ... RS __________________________________________________ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
